Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
  • D21F11/14—Making cellulose wadding, filter or blotting paper

Definitions

• the present invention relates to an apparatus for loosening the fibres of a raw tissue web before converting to the tissue product and to a corresponding method.
• a raw tissue web is a continuous tissue paper and tissue paper is defined as a soft absorbent paper having a low basis weight.
• tissue paper is defined as a soft absorbent paper having a low basis weight.
• the total basis weight of multiple-ply tissue products is preferably equal to a maximum of 65 g/m2, more preferably to a maximum of 50 g/m ⁇ .
• Its density is typically below 0.6 g/cm ⁇ , preferably below 0.30 g/cm 3 and more preferably between 0.08 and 0.20 g/cm 3 .
• tissue is distinguished from paper production by the its extremely low basis weight and its much higher tensile energy absorption index (see DIN EN 12625-4 and DIN EN 12625-5) .
• Paper and tissue paper also differ in general with regard to the modulus of elasticity that characterizes the stress-strain properties of these planar products as a material parameter.
• a tissue's high tensile energy absorption index results from the outer or inner creping.
• the former is produced by compression of the paper web adhering to a dry cylinder as a result of the action of a crepe doctor or in the latter instance as a result of a difference in speed between two wires ("fabrics") .
• fabrics two wires
• Moist tissue paper webs are usually dried by the so-called Yankee drying, the through air drying (TAD) or the impulse drying method.
• the fibers contained in the tissue paper are mainly cellulosic fibres, such as pulp fibers from chemical pulp (e.g. Kraft sulfite and sulfate pulps) , mechanical pulp (e.g. ground wood) , thermo mechanical pulp, chemo-mechanical pulp and/or chemo-thermo mechanical pulp (CTMP) . Pulps derived from both deciduous (hardwood) and coniferous (softwood) can be used. The fibers may also be or include recycled fibers, which may contain any or all of the above categories.
• chemical pulp e.g. Kraft sulfite and sulfate pulps
• mechanical pulp e.g. ground wood
• thermo mechanical pulp chemo-mechanical pulp and/or chemo-thermo mechanical pulp
• CMP chemo-thermo mechanical pulp
• Pulps derived from both deciduous (hardwood) and coniferous (softwood) can be used.
• the fibers may also be or include recycled fibers, which may contain any or
• the fibers can be treated with additives - such as fillers, softeners, such as quaternary ammonium compounds and binders, such as conventional dry-strength agents or wet-strength agents used to facilitate the original paper making or to adjust the properties thereof.
• additives such as fillers, softeners, such as quaternary ammonium compounds and binders, such as conventional dry-strength agents or wet-strength agents used to facilitate the original paper making or to adjust the properties thereof.
• the tissue paper may also contain other types of fibers, e.g. regenerated cellulosic fibres or synthetic fibers enhancing, for instance, strength, absorption, smoothness or softness of the paper.
• Tissue paper may be converted to the final tissue product in ⁇ many ways, for example, by embossing or laminating it into a multi-ply product, rolled or folded.
• raw tissue web in sense of the present invention it is meant the web discharged from the paper making machine before it is converted to the tissue product as before-mentioned.
• the fibres are arranged in a substantially oriented manner and the dried fibres form a fibre composite, namely the raw tissue web.
• the fibres in the raw tissue web leaving the paper-making machine are as previously mentioned substantially- oriented in the machine direction of the paper-making machine, as it is also depicted in Fig. 5A, which schematically shows a raw tissue web after leaving the papermaking machine and before being treated by method of the present invention.
• Such a raw tissue web or tissue paper, respectively is depending on its basis weight relatively stiff and inflexible.
• the basic idea of the present invention is to loosen at least the fibres of the raw tissue web located in the surface region/-s of the tissue web so as to increase the softness on the surface of the raw tissue web and to break up the inflexible fibre composite of the raw tissue web, which is both achieved in that the raw tissue web is flexed in the machine direction and/or cross to the machine direction (cross-machine direction) .
• the flexing for example could be compared (merely for the sake of explanation of the invention) with pulling the raw tissue web over an edge under tension, whereby the fibres on the surface of the tissue web opposite to the surface facing the edge are raised.
• the apparatus comprises a first pair of rollers and/or a second pair of rollers.
• the first pair of rollers defines a first nip for introducing the tissue web, the first nip being at least as large as the thickness of the tissue web.
• the tissue web is introduced into the first nip in a machine direction preferably under tension.
• the tissue web is not compressed or calendared in the nip.
• the first nip equals the thickness of the tissue web or is slightly larger.
• One roller of the first pair of rollers has protuberances extending about the entire circumference of the roller and separated from each other in the longitudinal direction of the roller.
• the longitudinal direction of the roller is meant to be the direction parallel to the center axis of the roller.
• the other roller of the first pair of rollers is formed complementary to the one roller thereof.
• the other roller has protuberances extending about the entire circumference of the roller and being separated from each other in the longitudinal direction of the roller.
• the rollers are arranged so that the protuberances of the one roller engage with regions separating adjacent protuberances of the other roller, etc.
• the apparatus of the present invention may alternatively or additionally comprise a second pair of rollers defining a second nip for introducing the tissue web, the second nip being at least as large as the thickness of the tissue web.
• the second nip is defined and configured similar or equal to the first nip.
• one roller of the second pair of rollers has protuberances being at least separated in a direction of the circumference of the roller.
• protuberances in the form of columns or knobs having e.g. a rounded head are distributed about the circumference of the roller and separated from each other.
• the other roller of the second pair of rollers is also complementary to the one roller thereof. That is, the other roller is also configured to have protuberances being at least separated from each other in a direction of the circumference of the roller and both rollers are arranged so that the protuberances engage portions between two protuberances of the other roller adjacent in a direction of the circumference of the roller.
• the web introduced into the nip dimensioned as aforesaid in context with the first pair of rollers is flexed in the cross- machine direction.
• the web is flexed about an axis or a plurality of axis perpendicular to the machine direction or in parallel with the cross-machine direction.
• the arrangement of the apparatus according to the present invention enables to loosen the fibres at least on one surface of a tissue web so as to increase the softness of the surface/-s of the tissue web as well as the flexibility.
• the protuberances of the one roller of the first pair of rollers are separated by means of grooves extending about the entire circumference of the one roller and being complementary to the protuberances.
• This arrangement leads to an improved intermeshing between the two rollers and therefore, a more uniform flexing of the tissue web. This in turn leads to a more uniform flexibility and softness of the tissue web.
• the protuberances of the one roller of the second pair of rollers can be separated by means of grooves at least between the protuberances, the grooves extending in the longitudinal direction of the one roller and being complementary to the protuberances.
• the grooves are at least complementary to the two protuberances separated by the groove.
• the protuberances of the one roller of the second pair of rollers are separated in the longitudinal direction, so that the roller somewhat looks like an alternate arrangement of gear wheels and spacers on a common axis.
• a pair of calander rollers for calandering the tissue web after flexing and to improve its visual appearance.
• the protuberances on the one roller of the first pair of rollers are helically formed, being divided in the center of the roller as seen in the width direction of the center axis of the roller, the two parts running away from each other to the left side of the roller and to the right side of the roller, respectively, in the longitudinal direction of the roller.
• the roller is composed of two helically formed protuberances divided in the middle of the longitudinal direction of the roller.
• At least one of the rollers of the first and/or second pair of roller is heated.
• the protuberances and/or grooves of the one roller of the first and/or second pair of rollers and preferably also of the other roller are rounded.
• the protuberances have the dimensions of for example a micro-embossing used in converting.
• the protuberances of the one roller of the first and/or second pair of rollers have a width parallel to the width of the roller of approximately 0.2 to 1.0 mm and a height perpendicular to the width of approximately 0.2 to 1.0 mm.
• the dimensions of the first pair of rollers and second pair of rollers is the same.
• the width of the protuberances equals the height of the protuberances.
• the present invention also provides a method for loosing the fibres of a raw tissue web, the method comprising the steps of introducing the tissue web into a first nip as described above and flexing the tissue web in the machine direction in the first nip.
• the method may alternatively or additionally comprise the step of introducing the tissue web into a second nip similar to the one described above and flexing the tissue web in the cross-machine direction in the second nip.
• the method of the present invention also comprises the step of calandering the tissue web at least subsequent the first and/or second flexing.
• Fig. 1 shows schematically the apparatus according to one embodiment of the present invention
• Fig. 2 shows the section A of Fig. 1 in an enlarged scale, wherein the two rollers of the second pair of rollers is depicted;
• Fig. 3 shows a side view of the first pair of rollers shown in Fig. 1 in an enlarged scale
• Fig. 4 shows a cross section of the first pair of rollers perpendicular to the longitudinal direction of the one roller and the other roller;
• Fig. 5A and Fig. 5B show the raw tissue web being discharged from the paper making machine before the process of the present invention (Fig. 5A) and after the process of the present invention (Fig. 5B) .
• an apparatus comprising a first pair of rollers and a second pair of rollers.
• the first pair of rollers is located downstream the second pair of rollers in the machine direction MD.
• the second pair of rollers can be located downstream the first pair of rollers in the machine direction.
• the first pair of rollers has a first roller 3 and a second roller 4.
• the second pair of rollers has a first roller 5 and second roller 6. All rollers 3 to 6 are disposed with their axis of rotation or center axis, respectively in parallel with a raw tissue web 7 and transverse to the machine direction (in cross-machine direction) .
• the tissue web is transported preferably under tension in the machine direction.
• the first pair of rollers defines between the first roller 3 and the second roller 4 a first nip 8. Similar, the first roller 5 and the second roller 6 of the second pair of rollers 2, define a second nip 9. As shown in Fig. 1, the raw tissue web 7 (hereinafter tissue web 7) is transported in the machine direction.
• Fig. 2 shows the second pair of rollers including the first roller 5 and the second roller 6.
• the tissue web 7 is introduced into the second nip 9 and being transported in the machine direction MD.
• the first roller 5 of the second pair of rollers comprises protuberances 10 extending in the longitudinal direction of the roller 5, i.e. in parallel to the center axis.
• the protuberances 10 on the roller 5 are separated to each other by a groove 11 also extending in the longitudinal direction of the roller 5.
• the protuberances 10 could additionally be separated from each other in the longitudinal direction so that the roller would look similar to an alternate arrangement of gear wheels and spacers on a common axis.
• the second roller 6 of the second pair of rollers is configured complementary to the roller 5 as it is depicted in Fig. 2.
• the protuberances 10 of the roller 5 engage with grooves 11 of the roller 6 and vice versa. Consequently, if the tissue web 7 is passed through the second nip 9 in the machine direction, the tissue web is flexed about an axis in the cross machine direction, i.e. perpendicular to the machine direction.
• the first pair of rollers 1 is depicted by a side view in enlarged scale in Fig. 3 and in a cross section perpendicular to the longitudinal direction (longitudinal cross section) of the two rollers in Fig. 4.
• the first roller 3 of the first pair of rollers 1 has protuberances 12 extending about the entire circumference of the roller 3 and grooves 13 separating the protuberances 12 from each other in the longitudinal direction of the roller 3, the grooves 13 also extending about the entire circumference of the roller 3.
• the second roller 4 of the first pair of rollers 1 is configured complementary to the first roller 3.
• the second roller 4 also has protuberances 12 and grooves 13, wherein the protuberances 12 of the second roller 4 mesh with grooves 13 of the first roller 3 and vice versa. Consequently, and as depicted in Fig. 4 the tissue web 7 is flexed about an axis in parallel with the machine direction, which in Fig. 4 runs perpendicular to the drawing sheet. Please note that in Fig. 4 only half of the first roller 3 and the second roller 4 is depicted and the axes 14 and 15 represent the symmetry axis of the respective rollers.
• the protuberances 10 and 12 of the first and second pair of rollers preferably have a width W of between app. 0,2 and 1,0 mm and a height H of between app. 0,2 and 1,0 mm. More preferred the height H equals the width and the protuberances of the first pair of rollers have substantially the same dimensions as of the second pair of rollers.
• first nip 8 and the second nip 9 are configured as schematically depicted in the figures so as to be not smaller than the thickness of the tissue web 7.
• the dimension of the nips 8 and 9 is configured to be equal to the thickness or the tissue web 7 or slightly larger. This leads to the fact that the raw tissue web 7 introduced in the first and second nip 8, 9 is not damaged, no pattern is formed on the tissue web and the visual appearance is not inferred. To say it in other words, the tissue web is not calandered or compressed in the nips 8 and 9.
• Common thicknesses of raw tissue are approximately 150 to 400 ⁇ m, preferably 200 to 350 ⁇ m for TAD-Tissues, and approximately 80 to 200 ⁇ m, preferably 100 to 150 ⁇ m for tissues of the conventional drying method (Yankee-drying) . These data always refer to the thickness of one ply.
• a tissue web is comprised of a plurality of fibres upon being discharged from the paper making machine.
• the plurality of fibres are all oriented substantially in the machine direction MD as shown in Fig. 5A.
• the fibres 16 at least in the outer surface regions are raised so as to stand up and being not oriented in the machine direction MD anymore.
• the fibres 16 are also raised on the outer surfaces and are not oriented in the machine direction anymore, but parallel or angular to the cross machine direction.
• tissue product final tissue product
• the tissue web 7 produced by the present invention can be converted in any manner as it is known to the skilled person.

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• 2004
  • 2004-10-07 AT AT04790182T patent/ATE421612T1/de not_active IP Right Cessation
  • 2004-10-07 ES ES04790182T patent/ES2319773T3/es active Active
  • 2004-10-07 WO PCT/EP2004/011225 patent/WO2006037365A1/en active Application Filing
  • 2004-10-07 DE DE602004019257T patent/DE602004019257D1/de active Active
  • 2004-10-07 EP EP04790182A patent/EP1797239B1/de not_active Not-in-force

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